I just set up a new WordPress network site at the URL http://www.worldrevisited.net for which I want to use the Travel theme. However, after having copied the theme to its correct directory and want to activate it, the page remains entirely blank, and so does basically anything in WordPress (I can’t even access the admin dashboard after having activated the Travel theme). I can only regain access over WordPress when manually deleting the theme folder (and then switch back to the WordPress default theme manually). I tried copying the theme in its most current version to the correct folder via FTP several times, but the error stays the same.
I then – just for testing – created a second Network site in WordPress and activated the Travel theme there (http://www.worldrevisited.net/test/) and here it works perfectly well, while again trying the same in the main WordPress site (same WordPress installation, same theme folder – it is one WordPress setup) always leads to a blank white page.

What can I do to fix this? Is this a problem with the main WordPress network site not accepting Travel as a valid theme? (any other theme I have works there, only travel always fails)